Grade percent is rise ÷ run × 100
Drainage plans speak in grade percent: a <strong>2% grade drops 2 feet per 100 feet</strong> of run — the standard slope for yard drainage away from a foundation. The calculator converts any rise and run into percent, degrees and the ratio form (1:N) that site plans draw.
Where grade matters at home
Soil should fall 6 inches over the first 10 feet from a foundation (5%); sidewalks and patios slope 1–2%; accessible ramps max at 8.33% (1:12). Enter any two of rise, run or percent and the math checks whether your yard, drive or ramp meets the target.